How do i split an array in to quarters?

I need to:

Read the image file into Matlab. Split the array into quarters along the longer (628) axis. For the first quarter, generate a one-dimensional array containing the sum of the brightness of all the pixels in the now- quartered dimension, computed at each position in the shorter (470) dimension. This array should have 470 elements. Repeat this for the other three quarters.

I don't know how to split the array or the following steps

Help please

Answer 1

[Walter Roberson]

Q{1} = YourImage(1:end/2, 1:end/2);
Q{2} = YourImage(end/2+1:end, 1:end/2);

Likewise for the other two quarters.

Answer 2

[Image Analyst]

You forgot to tag it as homework, so I did it for you.

I'll assume the longer dimension is the x or columns dimension and it's a grayscale image. Then here's some hints

[rows, columns, numberOfColorChannels] = size(theImage);
% Get the middle 3 columns to divide the array at.
dividingCols = round([1,2,3] .* columns / 4)
% Do the third quarter. All rows in the third quarter lengthwise.
quarter3 = theImage(:, dividingCols(2):end);
theSum = sum(quarter3(:))